Hot topping method

ABSTRACT

A hot top method of the type in which reusable hot top casings are relined after each ingot casting. The relining is effected by advancing a plurality of casings in seriatim to fixed lining stations, at which an annular cavity is formed adjacent the inner surface of each casing, and then a slurry is fed into the cavity and the liquid carrier is withdrawn from the slurry to form a liner of solid materials on the inner surface of the casing. The slurry is formed by pulverizing a fibrous material and then mixing the pulverized fibrous material with a major proportion of a finely divided refractory material at a pre-mixing station located remotely from the fixed lining station. The dry pre-mix is then transported to the lining stations and mixed with a liquid carrier to form the desired slurry.

United States Patent 1 Jago et a1. July 31, 1973 [54] TOWING METHODFOREIGN PATENTS OR APPLICATIONS 1 1 lnvemorsl Edward John Jag", Berea,Ohio; 967,398 8/1964 Great Britain 164/33 Fred Eastwood, late of BayVillage, Ohio y f Primary Examiner-J. Spencer Overholser Donald Todlsh,Medma Ohm Assistant Examiner.lohn E. Roethel [73] Assignee: FosecoInternational Limited, Hubbard Leydlg, and 05mm Birmingham, England [22]Filed: Oct. 1, 1969 5 ABSTRACT [21 Appl. No.: 863,760 A hot top methodof the type in which reusable hot top casings are relined after eachingot casting. The relining is effected by advancing a plurality ofcasings in se- [g%] {15.8]. riatim to fixed lining Stations at which anannular nil. r "1.6.4,.- 3' is fomled adjacent the inner surface of eachcasing, 1 0 can 01 and then a slurry is fed into the cavity and theliquid carrier is withdrawn from the slurry to form a liner of 56 R fsolid materials on the inner surface of the casing. The I 1 e erencesslurry is formed by pulverizing a fibrous material and UNITED STATESPATENTS then mixing the pulverized fibrous material with a 2,81 1,45710/ 1957 Speil et a1. 106/69 major proportion of a finely dividedrefractory material 3,253,936 5/1966 Weindel 106/69 X at a pl'e-mixingstation located remotely from the fixed lining station. The dry pre-mixis then transported to or a eta 3,373,047 3/1968 Sheets et al 249 197 xggg g i ggz z gg mm a earner to 3,384,149 5/1968 Eastwood 164/332,811,457 10/1957 Speil et a1. 106/69 13 Claims, 3 Drawing FiguresPatented July 31, 1973 3,749,148

2 Sheets-Sheet 1 g3 H\\\\ Q 35 53 INVENTOR S FRED EASTWOOD EDWARD JOHNJAGO WALTER DONALD TODISH Patented July 31, 1973 3,749,148

2 Sheets-Sheet 2 F NVENTORS .2 FRED EASTWOOD EDWARD JOHN JAGO WALTERDONALD TODISH Arrvs.

HOT TOPPHNG METHOD CROSS-REFERENCE TO RELATED APPLICATION U.S.application Ser. No. 740,036, filed June 26, 1968, for Composition ForUse in Forming Heat Insulating Liners and Method for Making Same."

The present invention relates generally to the art of heat topping and,more particularly, to an improved hot topping method of the type whichinvolves repetitive in situ lining of reusable hot top casings.

In the casting of metal ingots, it is common practice to use a hot topmounted on or at the top of an ingot mould for the purpose of containingfeed or head metal and maintaining it molten while the metal in theingot mould is solidifying. The metal in the hot top is above and incontact with the metal in the ingot mould so that as the metal in theingot mould shrinks, the feed metal feeds down into the ingot body andthus prevents the formation of shrinkage cavities in the body of theingot.

The latest type of hot top in commercial use comprises a single metalcasting, preferably in the form of a one-piece casting, and a heatinsulating liner on the inner surface of the casing. The casing itselfis reusable, but the insulating liner must be replaced after each use,i.e., after the casting of each ingot. The liner is generally made of arelatively low cost composition having good heat insulating properties,the composition being preformed in self-supporting slabs or sleevesshaped to fit the particular casing in which they are to be used. Aftereach use of the hot top, the remnants of the used liner, which usuallydisintegrates to some extent during the casting operation, are thenremoved from the metal casing and replace-d by a new preformed liner.

Typically, the relining operation includes setting preformed liners inthe shape of individual slabs in the casing and driving four slabs downalong the four inside walls of the casing with the slabs being wedgedagainst each other in the corners so as to urge the slabs against thecasing walls.

Because this method, while a vast improvement over prior methods, isstill a time-consuming operation, considerable effort has been directedtowards developing a method which can form an insulating liner in situwith a configuration which renders the liner self-retaining against thehot top casing. One such method which is now in commercial use isdescribed in U.S. Pat. No. 3,384,149, issued May 21, 1968, entitledMethod For Forming Hot Top Liners, and assigned to the assignee of thisinvention.

In accordance with that method, a slurry of a refractory material, afibrous material and a liquid carrier such as water is fed into anannular cavity formed between the inner surface of the hot top casingand the outer surface of a perforated forming tool. The liquid carrieris withdrawn through the interior of the forming tool so as to build upa layer of the fibrous and refractory materials in the cavity. Theforming tool is then withdrawn from the casing in such a manner that thelayer of fibrous and refractory materials forms a liner on the innersurface of the casing.

The slurry used in forming the liner generally comprises about 80 to 90percent by weight of the liquid carrier. As disclosed in Davidson Re.U.S. Pat. No. 25,915, the organic fibrous material that is used may bemechanical pulp or pulp manufactured from Waste paper, and refractorymaterial in a finely divided state can be added to the pulp slurry toprovide the desired consistency. The pulp facilitates the binding of therefractory material and also provides the liner with a porosity whichsubstantially increases its insulation qualities.

Unfortunately, the users of hot tops almost uniformly do not havefacilities for carrying out mechanical pulping. Also, it would generallybe impractical to install all the facilities needed to form a slurrythat could be employed in the method for forming a liner in situ asdescribed in the hereinbefore identified patent. It is accordinglynecessary to transport or ship to the hot top user a sufficient amountof the liner composition for carrying out the several hundred or eventhousands of relining operations that may well take place in one day.Shipping a slurry composition containing about percent by weight of aliquid carrier such as water is obviously expensive and does not offer apractical solution to the problem of providing an economical source ofthe lining composition.

It is, therefore, a primary object of the present invention to providean improved hot topping method which permits both the preparation of thelining material and the lining operation to be carried out at theoptimum locations, thereby improving the efficiency of the overallsystem.

It is another object of the invention to provide such a method whichdoes not involve transporting any large volumes of liquid, and whichminimizes shipping and storage space requirements.

Other objects and advantages of the invention will become apparent fromthe following description and upon reference to the accompanyingdrawings, in which:

FIG. 1 is a perspective view of a hot top with one corner broken away toshow the internal structure;

FIG. 2 is an end view, partially in section, of a mechanism for formingthe insulating liner in the hot top of FIG. 1; and

FIG. 3 is a side elevation, partially in section of the mechanism ofFIG. 2.

One current method of lining reusable hot top casings in situ, i.e.,forming the linings in the casings in the mill where the ingots arepoured, is described in U.S. Pat. No. 3,384,149, owned by the assigneeof the pres ent invention. In that method, a plurality of reusable hottop casings are advanced in seriatim to a fixed lining station where aperforated forming tool is inserted in each casing so as to form anannular cavity between the inner surface of the casing and the outersurface of the forming tool. A pre-mixed slurry, typically containing80-90 percent water, is then fed into the cavity, and the water iswithdrawn through the interior of the perforated forming tool so as tobuild up a layer of the solid ingredients in the cavity. Finally, theforming tool is withdrawn in such a manner that the layer of solidmaterials forms a liner on the inner surface of the hot top casing, andthe casing is advanced from the lining station to a drying station wherethe liner is dried sufficiently to permit the use of the lined casing inthe casting of another ingot.

Turning now to the drawings, in FIG. 1 there is shown a hot top 10adapted to be mounted on the top of a bigend-up ingot mold, such as usedin the formation of steel ingots for example. The hot top serves todelay the solidification of the feed metal or head metal containedwithin it so that molten metal can feed downwardly into the main bodyportion of the metal ingot to compensate ingot. In the particularembodiment illustrated, the hot top includes a one-piece outside metalcasing 11, with the lower portion of the outside surface of the casing11 being complementally formed with respect to the inside walls of aningot mold so that the lower portion of the hot top can extend down intothe upper portion of the mold.

For the purpose of initially mounting the hot top on the lip of abig-end-up mold, an outwardly projecting flange 12 is formed at aboutthe midpoint of the casing so that the hot top can be set on a pluralityof wooden blocks spaced around the lip of the mold. The metal casing 11is also provided with a pair of trunnions 13 located about halfway upthe casing for use in inverting the casing, and another pair oftrunnions 14 for lifting the hot top.

In order to provide the thermal insulation required to delaysolidification of the molten metal in the hot top during the casing ofan ingot, the metal casing 11 is lined on the inside with a thin layer15 having low thermal conductivity. To provide the required thermalinsulation, the liner material preferably has a mean heat diffusivityvalue over the temperature range of 25 to 1500 C. of below about 0.015centimetergram-second units. The term heat diffusivity is defined as VKc p wherein X is the thermal conductivity of the material, c is thespecific heat, and p is the density. Suitable highly thermallyinsulating compositions are those described in the Davidson patents Re.US. Pat. Nos. 25,905 and Re. 25,915. The thickness of the liner can varyfor different applications, but in general it should be between about0.5 inch and about 1.5 inches.

If desired, a refractory bottom ring may be secured to the lower end ofthe metal casing 11 for the purpose of preventing the creepage of moltenmetal up behind the insulating liner 15 and to protect the lower end ofthe casing 11. In the illustrative embodiment, however, the bottom ringis obviated by use of an insulating liner which wraps around the lowerend the casing, whereby the liner itself serves the purpose of thebottom ring. However, where it is desired to use a bottom ring insteadof a wrap around-type liner, a conventional sand ring may be used andheld to the casing by means of conventional spring clips. Also, aconventional wiper strip may be fitted over the lower outside corner ofthe hot top, extending entirely around the hot top with the upper end ofthe wiper strip bent outwardly to bear against the mold wall to preventthe molten metal from rising in the gap between the hot top and themold.

In a typical steel mill, ingots are cast in large batches, or heats."Thus, every time the ingots in a given heat are stripped from the moldsin which they are cast, an equal number of hot top casings must berelined before they can be reused in the casting of another heat ofingots. Of course, one of the necessary steps in the relining operationis removal of the residue from the previous liner; the liners usuallydisintegrate during the casting operation, but sometimes there is stilla residue of the used liner which clings to the hot top casing and mustbe removed therefrom, before a new liner can be applied.

The magnitude of the problem posed by the necessity of relining the hottop casings after each use will be readily appreciated when it isrecognized that hundreds or even thousands of ingots are cast every dayin a modern steel mill. In the lining method illustrated in FIGS.

2 and 3, which is described in more detail in the aforementioned U.S.Pat. No. 3,384,149, a plurality of onepiece hot top casings 11, fromwhich the residue of the previously used liner has already been removed,are transported in seriatim by means of a roller conveyor 20 to a fixedlining station including a casing table indicated generally at 21. Thecasings 11 are inverted before they arrive at the lining station'so thatthe wider end of the hot top opening is at the top of the casing as itenters the lining station. The casing table 21 includes a centralsupport plate 22 which is covered with a sealing gasket 23, and both theplate 22 and the gasket 23 are large enough in diameter to overlap theedges of the casing opening. As a casing 11 enters the lining station,it rides over a plurality of rollers 24 which are mounted in verticallymovable brackets 25 in a channel formed in the table adjacent the mainsupporting plate 22. After the casing 11 has reached a center positionon the table 21, the rollers 24 are lowered by lowering the brackets 25so that the casing comes to rest on the sealing gasket 23 on top of thecentral support plate 22.

After the casing 11 has come to rest on the sealing gasket 23 bylowering of the rollers 24, the entire casing table 21 is raised intotelescoped relation with a liner forming tool 26 which is mounteddirectly above the table 21 in axial alignment therewith. Raising of thetable 21 is accomplished by means of a hydraulic piston 27 mounted onthe top end of a vertical piston rod 28 which extends downwardly into acylinder 29 connected to a suitable source of pressurized hydraulicfluid. The forming tool 26 is complementally formed with respect to theinterior of the hot top casing 11 so that after the casing 11 and thetool 26 have been moved into telescoped relationship with each other, anannular cavity is formed between the perforated outside walls of thetool 26 and the solid inside walls of the metal casing 11. Since thetool 26 and the casing l l are complementally formed with respect toeach other, this annular cavity will be of substantially uniform widtharound the entire circumference of the tool.

After the casing 11 and the forming tool 26 have been moved intotelescoped relationship, a slurry containing finely divided refractorymaterial, fibrous material, and a liquid carrier is fed into the annularcavity by means of a manifold assembly 30 extending around the top ofthe forming tool 26. The slurry is fed into the manifold assemblythrough a feed pipe 31 which conducts the slurry into an annularmanifold tube 32 having a plurality of inside ports 33 opening intocorresponding registering passageways 34 communicating with the annularcavity 35 between the casing 11 and the forming tool 26. In order toprevent any leakage of the slurry down along the outside walls of thecasing 11, an air filled sealing gasket 36 is mounted directly below theslurry passageways 34 for engaging the outer sur face of the hot topcasing 11 as it is moved into telescoped relationship with the formingtool 26. Air is supplied to the sealing gasket 36 through a pipe 37connected to a suitable source of pressurized air.

As the slurry enters the cavity 35 from the manifold assembly 30, theslurry flows downwardly into the cavity 35, which is closed at thebottom by means of the sealing gasket 34 bearing against the bottom ofthe forming tool, with the carrier liquid being extracted through theperforated walls of the hollow forming tool 26 so as to build up acomposite layer of the solid fibrous and refractory material on theouter surface of the tool. The liquid extraction through the perforatedwalls of the tool 26 is effected by a pressure differential which may beachieved by several different means. For example, the slurry suppliedfrom the inlet manifold 30 is ordinarily under a certain feed pressure,and this pressure itself is sufficient in certain cases to force thecarrier liquid from the cavity through the perforated walls into theinterior of the tool 26. In addition, a vacuum may be drawn on theinside of the tool 26 so as to increase the pressure differential acrossthe perforated walls and thereby enhance the extraction of carrierliquid therethrough.

As the carrier liquid is extracted through the perforated walls of theforming tool 26, the extracted liquid is collected inside the formingtool and discharged by gravity through a discharge port formed by anaperture in the bottom of the forming tool 26 and registering apertures41 and 42 formed in the sealing gasket 23 and the central support plate22. The discharged liquid then enters an effluent chamber 43 formed inthe bottom of the table 21 and then on out through a waste line 44.While the carrier liquid is being extracted through the perforated wallsof the forming tool 26, the solid fibrous and refractory material in theslurry are directed against the outer surface of the forming tool, withthe fibrous material quickly building up a random mat which acts as afilter to retain the finely divided refractory material within the linercavity 35 while permitting the carrier liquid to pass through into theinterior of the tool. Consequently, a composite layer of f1- brous andfinely divided refractory material builds up around the outer surface ofthe forming tool 26 until it completely fills the annular cavity 35,thereby forming a green" liner on the inner surface of the hot topcasing 11.

After the liner cavity 35 has been filled with the composite layer offibrous and refractory material, and sufficient carrier liquid has beenextracted therefrom to enable the green liner to maintain its integrityon the casing walls, the forming tool and the lined casing are movedrelatively away from each other, and the casing is transferred to adrying station to dry the green liner before it is used in the castingof another ingot. In order to break the green liner loose from the outersurface of the forming tool before the tool and the casing aretelescoped away from each other, compressed air is admitted into theinterior of the forming tool 26 just before the casing table 21 isretracted away from the forming tool 26. This compressed air applies abrief burst of pressure against the inner surface of the green liner,through the perforated walls of the tool, so as to break the green lineraway from the forming tool. Alternatively, other suitable means, such asa collapsible forming tool for example, may be used to break the lineraway from the forming tool before the tool and the casing are movedrelatively away from each other.

In order to transfer the lined casing away from the lining station afterthe table assembly 21 has been lowered to its fully retracted position,the transport rollers 24 are raised into engagement with the lower endof the hot top casing so as to raise the casing slightly off the sealinggasket 23. The casing is then transferred onto a continuation of theroller conveyor 20 which transports the casing and the green linertherein to a drying station where the green liner is dried sufficientlyto permit the casting of molten metal in the lined casing. The dryingstation may take the form of a conventional drying oven or any othersuitable drying means.

To form a self-retaining liner, the illustrative hot top casing 11 isprovided with a pair of peripheral recesses or grooves 51 and 52extending completely around the inner surface thereof. Consequently,when the insulating liner is formed in situ as shown in FIG. 3, therecesses 51 and 52 form a part of the annular cavity 35 and thus thecomposite layer of refractory and fibrous material which fills thecavity projects into these recesses 51, 52. In other words, theinsulating liner is always complementally formed with respect to theinner surface of the hot top casing Ill, and thus any recesses formed inthe inner surface of the casing will be occupied by complementallyformed projections on the liner which is formed in situ. In theparticular configuration illustrated, the two grooves 51, 52 areoccupied by complementally formed ribs 53, 54 which serve to preventaxial movement of the liner within the casing. Of course, axial movementof the insulating liner within the casing is not a problem as long asthe casing remains in the inverted position shown in FIGS. 2 and 3, butthe casing naturally must be inverted at some subsequent point before itis mounted on top of an ingot mold, and it is then that the retainingribs 53, 54 serve to retain the liner within the inverted casing.

In accordance with the present invention, a relatively dry pre-mix forthe slurry used in the in situ formation of hot top liners is formed ata station located remotely from the lining station by pulverizing in arelatively dry environment at least one fibrous material, and thenmixing the pulverized fibrous material with a major porportion of afinely divided refractory material in the presence of sufficient liquidto prevent dusting. This dry pre-mix is then transported to the remotelylocated lining station at the steel mill where it is blended with wateror other suitable liquid carrier to form a slurry for use in the in situhot top lining method. This method provides significant economicadvantages in that the solid ingredients of the lining composition maybe prepared at a single pre-mixing station for a number of differentremotely located steel mills. Thus, the solid ingredients for the liningslurry may be prepared at a single mechanical pulping facility, forexample, and then transported to the different steel mills where thewater or other carrier liquid is blended with the pre-mixed solidingredients. Since the water typically comprises about percent by weightof the slurry, it can be seen that significant savings in shipping andstorage space and costs, as well as handling costs, are realized. Andyet the quality of the hot top liners produced by this technique hassurprisingly been found to be equal or even superior to the quality ofliners prepared from a slurry in which the fibrous material is pulped inthe carrier. In this connection, it should be noted that attempts havebeen made heretofore to form apulp slurry by reducing the water contentbelow about 50 percent by weight, but it was found that caking andagglomeration of the fibers resulted. Pulp slurries have also beenprepared in the usual manner and then dried to remove a substantialportion of the water, but in this case the subsequent addition of waterto the dried pulp slurry required that a mechanical dispersing step,similar to the mechanical pulping itself, be carried out.

The pulverizing operation in the present method can be carried out in aconventional hammer mill, ball mill or the like. The fibrous ingredientsare thereby reduced to short lengths or flakes that are later amenableby subsequent mixing with a liquid carrier to form a dispersion withoutthe necessity of employing excessive energy such as is required to breakup an agglomerated fibrous mixture. By way of illustration, it has beenfound suitable to equip a hammer mill or ball mill with a screen havingopenings from about Ma inch to ii: inch. The pulverized materialobtained from such mills are not individual elements but are usuallypresent as a conglomeration of several fibers. A size of about 1 to 3millimeters generally characterizes the pulverized material. While it isdesirable to pulverize all fibrous components in accordance with thisinvention, any fbrous material (such as asbestos) that can be purchasedin a pulverized state need not be further processed.

The improved heat insulating composition of this invention comprises byweight, pulverized organic fiber present in an amount from zero percentto about percent, pulverized inorganic fiber present in an amount fromzero percent to about 40 percent, refractory aggregate present in therange of from about 50 percent to about 90 percent, and sufficientliquid carrier to prevent dusting. A range of from about one percent toabout 20 percent by weight has been found to be suitable for thecarrier. Optionally, a binder for the other components may be added inan amount of up to about 20 percent. The particular proportion ofinorganic fibrous material and organic fibrous material that areemployed may be varied to provide the degree of insulation andformability desired. Indeed, depending on the properties desired, it maybe necessary to employ only a single fibrous material, i.e., eitherorganic or inorganic. However, the total of the fibrous ingredientsshould not be lower than a minimum of five percent by weight and amaximum of about 50 percent by weight to insure good permeability andinsulation but retain minimal penetration by the molten metal.

With regard to the specific materials that are used for the componentsof the present composition, any refractory material previously used forhot top liners may be employed. Suitable examples include alumina,silica, aluminum silicates, magnesium silicate, chromite, zirconia, ballmill dust, zirconium silicate, and magnesium oxide,. Among the inorganicfibrous materials that may be used are asbestos, slag wool, aluminumsilicates and silica. For the organic fibrous material, any animal orvegetable fibrous material may be used as can synthetic organiccompositions such as rayon and nylon. Suitable examples inclue paper,waste paper or other cellulosic fibrous materials.

The type of binder that is used and the weight percentage that isemployed will be in large part dictated by the particular type offorming operation used for the liner. Indeed, in some instances, asufficient bond is obtained from the entwining of the fibrous materialand additional binder need not be included. When drying temperaturesbetween 250 and 450 F. are maintained, suitable binders include ureaformaldehyde and phenol formaldehyde resins. When drying temperatureslower or higher than the previous range are used, binders such ascolloidal silica, aluminum orthophosphate, sodium silicate and epoxyresins can be employed.

Colloidal silica may be used where a low residual gas content isdesired. Aluminum phosphate and colloidal silica can also be employedwhere molds hotter than 450 F are encountered. Epoxy and other resinscapable of setting without heat after addition of a catalyst oraccelerator can be employed where molds have temperatures below thatnecessary to harden other types of binders.

Typically, the liquid carrier that is utilized for the other componentsof the composition will be water. However, any organic compounds notinsoluble with water and having a high evaporation rate at the dryingtemperature can be employed if production conditions allow. Whenorganiccompounds are used, forced air or vacuum drying combined with acondensing system for solvent recovery are economically desirable.Suitable organic compounds include various alcohols, naphthas,chlorinated hydrocarbons and ketones.

After pulverizing the fibrous material and mixing the same with thedesired amounts of refractory material, binder and liquid carrier, theresulting mixture may be shipped or otherwise transported to a remotelining location where the liner is to be formed in the hot top casings.At the location of the lining station, liquid carrier (not necessarilythe same as the one already present) is added to the shipped compositionwith slight mixing, to form a slurry that may have, for example, 80 to95 percent by weight liquid carrier. The slurry can then be used in themethod described above and illustrated in FIGS. 2 and 3.

The invention may be further illustrated by means of the followingexamples which are intended to be illustrative and not in limitation ofthe scope of the present invention. Unless otherwise indicated, allparts or percentages are by weight.

The properties referred to in the ensuing Examples were determined asfollows:

Dispersion time: The time required to obtain a homogeneous slurry.

Forming time: The time required to filter 600 cc. of slurry through a 60mesh screen at 45 p.s.i., which forms a pad built up on the screen.

Green water: The weight percentage of liquid carrier in the paddescribed in connection with forming time. Green permeability: A 2 inchdiameter specimen is cut from the pad using a rotating blade mounted ina conventional drill press. The specimen is measured and then mounted ina permeability specimen tube described in Section 7, page 13 of theAmerican Foundrymen's Society Foundry Sand Handbook and is tested forpermeability by following the procedure set forth on pages 2 through 4of the same publication. Dry permeability: This is carried out in amanner identical to Green permeability but is determined from a samplethat has been dried at 395 F. for 2 hours. Dry density: The weight perunit volume of the sample dried as described in connection with the drypermeability.

The binder used in Examples 3 through 5 was a phenol formaldehyde resin(composition number 2320 from Varcum Chemical Co.). About 13 to 15percent by weight of hexamethylenetetramine is included. The resin hasan inclined flow of 15 to 20 mm. at C. A typical screen analysis is asfollows: ml, +200- about one percent, and 200-about 99 percent minimum.The resin is commonly employed as a solid shell core binder in the metalcasting industry.

Example 1 A heat insulating composition containing less than at leastabout 20 percent water was attempted to be formed by pulping and thendrying the pulp slurry.

A V4 inch layer, 12 X 3 inches, of a waste newsprint mechanical paperslurry (five percent solids) was placed on a 60 mesh screen and allowedto air dry at a temperature of about 100 C. for 24 hours. After thistime, the paper was substantially dry, a hard shell having been formedon the exterior of the dried slurry.

The dried pulped paper was broken'up into pieces and stirred into 3 95gallons of water. A conventional Lightnin mixer, using a single bladeand operating at about 75 R.P.M. was employed. After 8 hours very littlepaper went back into its fibrous state. 1 inch pieces of paper and layerwere still present. After 24 hours, small pieces of paper approximatelyVs to 56 inch were still present Example 2 A composition as in Example 1was attempted to be prepared by partially drying a pulp slurry.

Three pounds of a five percent waste newsprint pulp slurry was weighedout and placed upon a cylindrical shaped screen (6 diam. X 4 incheshigh) to allow drainage.

Drainage was slow; and, after 24 hours, only 16 ounces from a total ofabout 45 ounces had been drained. The dimensions of the slurry beforedrainage was approximately 6 inches diam. X 2 16 inches thick (volume 71cubic inches). After drainage the thickness was 2 inches (volume 57cubic inches).

Example 3 A heat insulating composition containing less than about 20percent water was formed by ball milling in accordance with the presentinvention. Water was then added to form a slurry that can be used toform a hot top liner. The resulting composition was compared to anidentical formulation made by adding the other components to amechanical pulp slurry.

A sample of waste newsprint was passed through a conventional hammermill having a 3/16 inch screen opening. The collected shredded orpulverized product was added to the composition set forth in Table 1 bymixing with a Day Ribbon Blender:

TABLE 1 Component Per Cent Silica sand (20+300 mesh) 87.5 Pulverizedasbestos fiber 1.5 Waste newsprint 6.5 Binder 4.5

Total 100.0

During the mixing, about 17 percent water to reduce dusting was added tothe formulation hereinbefore described.

After being allowed to stand for 24 hours, the mixture was dispersed insufficient water to provide a solids content of 17 percent. Theproperties of the composition formed in accordance with this inventionwas compared to a standard having an identical formulation which wasprepared by adding the silica sand, asbestos fiber, binder andadditional water to a five percent paper slurry to form a 17 percentsolids slurry.

Test pads were made by filtration at 45 psi. through a 60 mesh screen.The results are shown in Table 2:

TABLE 2 Properties Standard Present lnvention Dispersion time required30 minutes 2 minutes Forming time 23 seconds 23 seconds Green water 34.423.l Green permeability 1.2 units 3.0 units Drying time required 2 hoursl-l V: hours Dry permeability 4.8 units 3.7 units Dry density 0.88gms/cc. 0.87 gms/cc.

"20 minutes to pulp paper and I0 minutes thereafter to form thedispersion.

EXAMPLE 4 Example 3 was repeated except that the paper employedconsisted of waste cardboard boxes.

The results are shown in Table 3:

TABLE 3 Properties Standard Present invention Dispersion time required30 minutes 2 invention Forming time 23 seconds 23 seconds Green water34.4 20.5 Green permeability 1.2 units 2.0 units Drying time required 2hours l 3'; hours Dry density 0.88 gms/cc. 0.89 gms/cc.

"20 minutes to pulp paper and 10 minutes thereafter to form thedispersion.

Example 5 A heat insulating composition as in Example 3 was formed byusing only inorganic fibrous elements. These elements were hammer-milledusing a V4 inch mesh screen and the collected product was dispersed intoa composition formulated as in Table 4 below by mixing with a Day RibbonBlender:

TABLE 4 Component Percentage Silica sand (20+300 mesh) 83 Asbestos fiber6 Slag wool 5 Binder 6 Total TABLE 5 Properties Standard PresentInvention Dispersion time required l0 minutes 2 minutes Forming time 23seconds 23 seconds Green water l9.l l8 Green permeability 2.4 units 3.5units Drying time required 1 A hours 1 A hours Dry density 0.96 gms/cc.0.98 gms/cc.

From Examples 1 and 2, it can be seen that the use of a pulp slurry thatis dried to reduce the water content' does not provide a practicalsolution to forming a composition for use in making a heat insulatingliner which contains a minimum amount of water for shipping yet whichcan be readily dispersed to form a slurry. Not only is the time requiredto reduce the water content prohibitively long but the dried,agglomerated product can only be re-dispersed into its fibrous stateafter an excessive amount of time, even with extreme mechanical stirringbeing used.

In contrast, Examples 3 through 5 demonstrate that the pulverized, lowliquid carrier composition has properties that are equal to or superiorto those achieved by the standard method of forming a slurrycomposition, i.e., prepared directly by pulping in water. Indeed, therelatively low dispersion time and the low green water contentcharacterize a composition that can be economically used to form a hottop liner.

The term pulverized, as used in connection with the present invention,is meant to define the degree of fibrillization and comminution producedby mechanically working the organic and inorganic fibrous materials by,for example, ball milling or hammer milling. The pulverized productproduced by mechanically tearing the fibrous materials will be light andfluffy resembling down feathers or snow flakes yet will still beparticulate and capable of screening into definite size fractions by anyof the standard screening procedures such as, for example, ASTM.Individual feahers or flakes are capable of passing a 56 inch screen butprobably would not pass a ,4; inch screen. In contrast to mechanicalpulping using water or another similar carrier, the pulverizingoperation should take place in a relatively dry state (i.e.,sufficiently dry to avoid caking or balling of the pulverized product,so that the fibers may be later dispersed in a liquid carrier withoutrequiring excessiveenergy. In most applications it has been found thatthe water or other liquid carrier content should be maintained less thanabout three percent by weight during the pulverizing".

I claim as my invention:

1. A method of forming heat insulating liners in a plurality of hot topcasings used with ingot molds, said method comprising the steps ofpulverizing in a relatively dry environment at least one fibrousmaterial, mixing the pulverized fibrous material with a major proportionof a finely divided refractory material in the presence of sufficientliquid to prevent dusting and to form a dry pre-mix for forming a heatinsulating composition, transporting the resulting composition to afixed lining station at a location remote from the site of thepulverizing and mixing steps, adding a liquid carrier to said drypre-mix at said lining station to form a slurry, advancing a pluralityof hot top casings in seriatim to said lining station, forming anannular cavity adjacent the inner surface of the casing, feeding theslurry into the cavity and withdrawing the liquid carrier from theslurry so as to form a liner of the fibrous and refractory materials onthe inner surface of the casing, and advancing each casing away from thelining station and drying the liner therein sufficiently to permit thecasting of molten metal in the lined casing.

2. A method of forming heat insulating liners as set forth in claim 1wherein said dry pre-mix comprises, by weight, zero percent to about 20percent of a pulverized organic fibrous material, zero percent to about40 percent of a pulverized inorganic fibrous material, about 50 percentto about 90 percent of a particulate refractory material, and a liquidcarrier present in an amount sufficient to prevent dusting, with theprovisio that the total per cent of the pulverized organic and inorganicfibrous materials is from about five percent to about 50 percent.

3. A method as set forth inclaim 2 wherein said dry pre-mix includes upto about 20 percent by weight of a binder.

4. A method as set forth in claim 2 wherein said refractory material isa member selected from the group consisting of silica, alumina, aluminumsilicates, magnesium silicate, chromite, zirconia, ball mill dust,zirconium silicate, magnesium oxide and mixtures thereof.

5. A method as set forth in claim 2 wherein said inorganic fibrousmaterial is a member selected from the group consisting of asbestos,slag wool, aluminum silicates, silica and mixtures thereof.

6. A method as set forth in claim 2 wherein said organic fibrousmaterial is a member selected from the group consisting of animalfibrous materials, vegetable fibrous materials, cellulosic fibrousmaterials, rayon, nylon and mixtures thereof.

7. A method of forming heat insulating liners in a plurality of hot topcasings at each of a plurality of steel mills, said method comprisingthe steps of pulverizing in a relatively dry environment at least onefibrous material, mixing the pulverized fibrous material with a majorproportion of a finely divided refractory material to form a dry pre-mixfor forming a heat insulating composition, said pulverizing and mixingsteps being carried out at a single mixing station, transporting theresulting pre-mix from said mixing station to a plurality of fixedlining stations at a plurality of steel mills located remotely from saidmixing station, adding a liquid carrier to said dry pre-mix at each ofsaid lining stations to form a slurry, advancing a plurality of hot topcasings in seriatim to each of said lining stations, forming an annularcavity adjacent the inner surface of each cas ing, feeding the slurryinginto the cavity and withdrawing the liquid carrier from the slurry so asto form a liner of the fibrous and refractory materials on the innersurface of the casing, and advancing each casing away from therespective lining station and drying the liner therein sufficiently topermit the casting of molten metal in the lined casing.

8. A method as set forth in claim 1 wherein said pulverized fibrousmaterial is pulverized to a size within the range of from about Imillimeter to about 3 millimeters.

9. A method as set forth in claim 1 wherein said pulverized fibrousmaterial is capable of passing a V2 inch screen but not a Vs inchscreen.

10. A method as set forth in claim 1 wherein said dry pre-mix containsfrom about one percent to about 20 percent by weight liquid.

1 l. A method as set forth in claim 1 wherein said dry pre-mix containsfrom about five percent to about 50 percent by weight pulverized fibrousmaterial.

12. A method as set forth in claim 1 wherein said slurry contains fromabout percent to about percent by weight liquid carrier.

13. A method of forming heat insulating liners in a plurality of hot topcasings used with ingot molds, said method comprising the steps ofpulverizing in a relatively dry environment at least one fibrousmaterial to a size within the range of from about 1 millimeter to about3 millimeters, mixing the pulverized fibrous material with a majorproportion of a finely divided refractory material in the presence offrom about one percent to about 20 percent by weight liquid to preventdusting and to form a dry pre-mix containing from about five percent toabout 50 percent by weight of said pulvercasing, feeding the slurry intovthe cavity and withdrawing the liquid carrier from the slurry so as toform a liner of the fibrous and refractory materials on the innersurface of the casing, and advancing each casing away from the liningstation and drying the liner therein sufficiently to permit the castingof molten metal in the lined casing.

2. A method of forming heat insulating liners as set forth in claim 1wherein said dry pre-mix comprises, by weight, zero percent to about 20percent of a pulverized organic fibrous material, zero percent to about40 percent of a pulverized inorganic fibrous material, about 50 percentto about 90 percent of a paRticulate refractory material, and a liquidcarrier present in an amount sufficient to prevent dusting, with theprovisio that the total per cent of the pulverized organic and inorganicfibrous materials is from about five percent to about 50 percent.
 3. Amethod as set forth in claim 2 wherein said dry pre-mix includes up toabout 20 percent by weight of a binder.
 4. A method as set forth inclaim 2 wherein said refractory material is a member selected from thegroup consisting of silica, alumina, aluminum silicates, magnesiumsilicate, chromite, zirconia, ball mill dust, zirconium silicate,magnesium oxide and mixtures thereof.
 5. A method as set forth in claim2 wherein said inorganic fibrous material is a member selected from thegroup consisting of asbestos, slag wool, aluminum silicates, silica andmixtures thereof.
 6. A method as set forth in claim 2 wherein saidorganic fibrous material is a member selected from the group consistingof animal fibrous materials, vegetable fibrous materials, cellulosicfibrous materials, rayon, nylon and mixtures thereof.
 7. A method offorming heat insulating liners in a plurality of hot top casings at eachof a plurality of steel mills, said method comprising the steps ofpulverizing in a relatively dry environment at least one fibrousmaterial, mixing the pulverized fibrous material with a major proportionof a finely divided refractory material to form a dry pre-mix forforming a heat insulating composition, said pulverizing and mixing stepsbeing carried out at a single mixing station, transporting the resultingpre-mix from said mixing station to a plurality of fixed lining stationsat a plurality of steel mills located remotely from said mixing station,adding a liquid carrier to said dry pre-mix at each of said liningstations to form a slurry, advancing a plurality of hot top casings inseriatim to each of said lining stations, forming an annular cavityadjacent the inner surface of each casing, feeding the slurrying intothe cavity and withdrawing the liquid carrier from the slurry so as toform a liner of the fibrous and refractory materials on the innersurface of the casing, and advancing each casing away from therespective lining station and drying the liner therein sufficiently topermit the casting of molten metal in the lined casing.
 8. A method asset forth in claim 1 wherein said pulverized fibrous material ispulverized to a size within the range of from about 1 millimeter toabout 3 millimeters.
 9. A method as set forth in claim 1 wherein saidpulverized fibrous material is capable of passing a 1/2 inch screen butnot a 1/8 inch screen.
 10. A method as set forth in claim 1 wherein saiddry pre-mix contains from about one percent to about 20 percent byweight liquid.
 11. A method as set forth in claim 1 wherein said drypre-mix contains from about five percent to about 50 percent by weightpulverized fibrous material.
 12. A method as set forth in claim 1wherein said slurry contains from about 80 percent to about 95 percentby weight liquid carrier.
 13. A method of forming heat insulating linersin a plurality of hot top casings used with ingot molds, said methodcomprising the steps of pulverizing in a relatively dry environment atleast one fibrous material to a size within the range of from about 1millimeter to about 3 millimeters, mixing the pulverized fibrousmaterial with a major proportion of a finely divided refractory materialin the presence of from about one percent to about 20 percent by weightliquid to prevent dusting and to form a dry pre-mix containing fromabout five percent to about 50 percent by weight of said pulverizedfibrous material for forming a heat insulating composition, transportingthe resulting composition to a fixed lining station at a location remotefrom the site of the pulverizing and mixing steps, adding a liquidcarrier to said dry pre-mix at said lining station to form a slurryContaining from about 80 percent to about 92 percent by weight of saidliquid carrier, advancing a plurality of hot top casings in seriatim tosaid lining station, forming an annular cavity adjacent the innersurface of the casing, feeding the slurry into the cavity andwithdrawing the liquid carrier from the slurry so as to form a liner ofthe fibrous and refractory materials on the inner surface of the casing,and advancing each casing away from the lining station and drying theliner therein sufficiently to permit the casting of molten metal in thelined casing.